State and federal agencies set smoothness or road profile requirements for roads such as highways and airport runways. Roads must be measured after construction to verify that the requirements have been met. Paved roads are also measured prior to being overlaid to determine the fill depth of new pavement at each point.
A road profile can be measured with traditional surveying equipment. This method is entirely manual and extremely slow.
Apparatus and methods have been devised that use accelerometers or inclinometers to measure the profile of a road. In each of these apparatus and methods surface deviations are measured as acceleration normal to the road surface. The measurements are dependent on the speed and acceleration of the apparatus and the slope of the road. The methods associated with these apparatus involve complex calculations and filtering to convert the measured acceleration into a surface profile. The apparatus must be maintained at a constant speed during measuring so the road portions covered during acceleration and deceleration are not measured.
Prior known devices for measuring the profile of a road include single beam profilographs. These devices have an elongated beam supported at each end by a wheeled truck or bogie. A center profiling wheel directly measures deviations in the road providing higher accuracy and less complexity than the profiling devices with accelerometers. These devices are manually pushed or pulled along a road. Measurements for surface deviation and distance are manually read and recorded. Although faster than surveying, these devices are slow.
Prior known beam profilographs have a fixed rear bogie and a castered front bogie. On curving roads the path traveled by the profiling wheel is neither the path of the front bogie nor the path of the rear bogie. A single path is measured at a time. Synchronization of the profiles for both sides of a lane for a paving machine is difficult. Since these devices are manually pushed or pulled the operator may be exposed to traffic.